Fabric heating/warming articles are known, e.g., in the form of electric blankets, heating and warming pads and mats, heated garments, and the like. Typically, these heating/warming articles consist of a fabric body defining one or a series of envelopes or tubular passageways into which electrical resistance heating wires or elements have been inserted. In some instances, the electric resistance heating wires are integrally incorporated into the fabric body during its formation, e.g. by weaving or knitting. Relatively flexible electric resistance heating wires or elements, e.g. in the form of a core of insulating material, e.g. yarn, about which is disposed an electrical conductive element, e.g. a helically wrapped metal wire or an extruded sheath of one or more layers of conductive plastic, have been fabricated directly into the woven or knitted structure of a fabric body.
According to one aspect of the invention, a method of forming a fabric article adapted to generate heat upon application of electrical power comprises the steps of: joining, in a continuous web, by a reverse plaiting circular knitting process, a stitch yarn and a loop yarn to form a fabric prebody, with the loop yarn overlaying the stitch yarn at a technical face and forming in loops at a technical back of the fabric prebody; at spaced-apart intervals during the knitting process, incorporating into the fabric prebody as the stitch yarn an electrical resistance heating element; transforming the fabric prebody into a fabric body, with the electrical resistance heating elements extending between opposite edge regions of the fabric body; finishing at least one of the technical face and the technical back of the fabric body, in a manner avoiding damage to electrical conductance of the electrical resistance heating elements, to form a fleece surface region; and providing conductor elements for connecting the electrical resistance heating elements to a source of electrical power.
Preferred embodiments of this aspect of the invention may include one or more of the following additional steps: finishing the technical face of the fabric body, in a manner to avoid damage to electrical conductance of the electrical resistance heating elements, to form a first fleece surface region, and/or finishing the technical back of the fabric body in a manner to avoid damage to electrical conductance of the electrical resistance heating elements to form a second fleece surface region; during or following the knitting process, applying, directly to the continuous web, the conductor elements for connecting the electrical resistance heating elements to a source of electrical power; incorporating into the fabric body conductive yarns comprising a core of insulating material, an electrical resistance heating element disposed generally about the core, and/or a sheath material generally surrounding the electrical resistance heating element and the core; connecting the conductor element to a source of electric power and generating heat, the source of electric power comprising alternating current or direct current, e.g. in the form of a battery, which may be mounted to the fabric article; limiting formation of loops to a central region of the fabric prebody, the central region disposed between a pair of edge regions in the fabric body, and providing the conductor elements for connecting the electrical resistance heating elements to a source of electrical power in the edge regions of the fabric body, or limiting formation of loops to a plurality of central regions of the fabric prebody, each of the plurality of central regions extending in a continuous web direction and being disposed between a pair of edge regions in the fabric body, and providing the conductive elements for connecting the electrical heating elements to a source of electrical power in the edge regions of the fabric body; separating the continuous web in a direction of the continuous web to form a plurality of discrete panels of limited width transverse to the continuous web direction, each of the discrete panels having a central region with loops disposed between edge regions with conductive elements; and severing the panels generally transverse to the continuous web direction to form discrete heating pad elements.
According to another aspect of the invention, a method of forming a fabric article adapted to generate heat upon application of electrical power comprises the steps of: knitting at least a stitch yarn to form a fabric prebody, the stitch yarn comprising an elastic yarn or fiber; at spaced-apart intervals, incorporating into the fabric prebody as the stitch yarn an electrical resistance heating element; transforming the fabric prebody into a fabric body, with the electrical resistance heating elements extending between opposite edge regions of the fabric body; and providing conductor elements for connecting the electrical resistance heating elements to a source of electrical power.
Preferred embodiments of both of these aspects of the invention may include the steps of rendering the yarns of the fabric body hydrophilic or hydrophobic.
According to still another aspect of the invention, a fabric article adapted to generate heat upon application of electrical power comprises a fabric body, incorporated into the fabric body, in the form of conductive yarn, a plurality of spaced apart electrical resistance heating elements extending generally between opposite edge regions of the fabric body, and electrical conductor elements extending generally along the opposite edge regions of the fabric body and adapted to connect the plurality of spaced apart electrical resistance heating elements to a source of electrical power.
Preferred embodiments of this aspect of the invention may include one or more of the following additional features. The electrical conductor elements are adapted for connecting the plurality of spaced-apart electrical resistance heating elements to a power source of alternating current or to a power source of direct current, e.g. a battery, which may be mounted to the fabric body. The fabric body comprises a knitted body, e.g. a reverse plaited circular knitted, or other circular knitted body (such as a double knitted body of two separate layers joined by interconnecting yarns, a single jersey knitted body, a two-end fleece knitted body, a three-end fleece knitted body, a terry knitted body, or a double loop knitted body), a warp knitted or weft knitted body, or a woven body. The fabric body comprises hydrophilic or hydrophobic material. The fabric body is formed by a stitch yarn and a loop yarn. The loop yarn overlays the stitch yarn at a technical face and forms loops at a technical back of the fabric prebody. The fabric prebody has loops formed only in a central region. The fabric body has fleece formed upon at least one, and preferably both, of the technical back and the technical face. The conductive yarn is a stitch yarn. The electrical conductor elements, at least in part, are applied as a conductive paste. Preferably, the electrical conductor elements comprise a conductive wire, or a conductive yarn or thread. The electrical conductor elements, at least in part, are applied as a conductive hot melt adhesive. The electrical conductor elements are attached upon a surface of the fabric body, e.g. by stitching, e.g. embroidery stitching, by sewing, by adhesive, by laminating, by mechanical fastening, or by strain relief fastening. The electrical conductor elements are incorporated into the fabric body, e.g. the fabric body is woven, e.g. plush woven or flat woven of coarse yarns that can be raised, and the electrical conductor elements comprise filling or warp yarns disposed at opposite edge regions of the fabric body. Preferably, the electrical conductor elements comprise at least two filling or warp yarns at each opposite edge region. The fabric body is weft or circular knit, and the electrical conductor elements comprise yarns disposed along opposite edge regions of the fabric body. Preferably, the electrical conductor elements comprise at least two yarns at each opposite edge region. The conductive yarn preferably comprises a core of insulating material, an electrical resistance heating element disposed generally about the core, and a sheath material generally surrounding the electrical resistance heating element and the core. The electrical resistance-heating element has electrical resistance in the range of about 0.1 ohm/cm to about 500 ohm/cm. In alternative embodiments of the conductive yarn, the core or the sheath material may be omitted. In a preferred embodiment, the fabric body comprises a first fabric layer and a second fabric layer, and the plurality of spaced apart electrical resistance heating/warming elements incorporated into the fabric body and the conductor elements are disposed generally between the first fabric layer and the second fabric layer. The fabric body comprises a double knit fabric body and the first fabric layer and the second fabric layer are joined, in face-to-face relationship, by interconnecting yarns, the plurality of spaced apart electrical resistance heating/warming elements incorporated into the fabric body and the conductor elements being positioned and spaced apart by the interconnecting yarns and joined by the conductors in a parallel circuit. The first fabric layer and the second fabric layer are formed separately and joined in face-to-face relationship, with the plurality of spaced apart electrical resistance heating/warming elements incorporated into the fabric body and the conductor elements disposed therebetween. The first fabric layer and the second fabric layer may be joined by laminating or by stitching. The plurality of spaced apart electrical resistance heating/warming elements and the conductor elements, arranged with symmetrical or asymmetrical spacing, are mounted upon a substrate, the substrate with the plurality of spaced apart electrical resistance heating/warming elements and the conductor elements mounted thereupon being disposed between the first fabric layer and the second fabric layer. The substrate comprises an open grid fabric or moisture resistant, vapor permeable polymeric barrier material. The plurality of spaced-apart electrical resistance heating/warming elements and the conductor elements are mounted upon at least one opposed surface of the first and second fabric layers, e.g., by stitching, e.g., embroidery stitching. The fabric article has the form of a heating pad. The knitted body is a weft or circular knitted body with stitch yarns comprising elastic yarns or fibers.
An objective of the invention is to provide electric heating/warming fabric articles, e.g. electric blankets, heating and warming pads, heated garments, etc., into which a plurality of spaced-apart electric resistance heating members, in the form of conductive yarns, are incorporated by a knitting or weaving process. The fabric body of the heating/warming article, including the incorporated electric resistance heating members, may subsequently be subjected to a fabric finishing process, e.g., one or both surfaces of the fabric body may be napped, brushed, sanded, etc., to form fleece. In a planar structure, such as an electric heating blanket, the electric resistance heating members are connected at their ends along opposite edge regions of the planar fabric body, i.e. of the blanket, and may be powered by alternating current or direct current, including by one or more batteries mounted to the blanket. The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.